The present invention relates to a tensioning device for a coil winding machine, which gives tension to a wire being wound.
A coil winding machine is used to wind a wire supplied from a supply bobbin around a coil bobbin, and it is usual that an adequate tensioning device is provided to give necessary tension to the wire being fed.
FIG. 1 shows a general configuration of such the conventional tensioning device for a coil winding machine. In the figure, a tensioning device 10 basically consists of a main tension pulley 14 to which a braking torque is applied, a back tension lever 15 which absorbs any fluctuation in the tension of the wire, and a pulley 17 mounted at a swinging end of the back tension lever 15, so as to give necessary tension to the wire drawn through the main tension pulley 14 and the pulley 17.
The main tension pulley 14 provides a constant breaking force to the wire by applying a magnetic force on a magnetic disc rotated integrally with the main tension pulley 14. In some devices, regulation of the braking torque is provided by regulation of the pressure of a band brake.
The wire 3, after passing around the main tension pulley 14, passes an idle pulley 18, the pulley 17 provided at the swinging end of the back tension lever 15, an idle pulley 4. It is a nozzle 5, and then wound by a bobbin 2 which is rotated with high speed by the coil winding machine 1. The nozzle 5 is movable by the coil winding machine 1 to right and left of the figure.
The back tension lever 15 is swingable about a supporting point 11, and with the aid of a tension spring 12 is given a rotating force in the clockwise direction thereby providing for absorption of fluctuation in the back tension and keeping a constant tension at the coil winding position.
In many of the then developed coil winding machines, a device is further provided for automatically binding a wire on a terminal pin mounted on the bobbin 2 before the ordinary coil winding operation. In these cases, the nozzle 5 is forced to make a complicated movement, and therefore if the above mentioned constant tension is continually applied to the wire, the coating of the wire strikes hard against the inlet (it being also an outlet) of the nozzle 5 and is broken away. It often occurs that after binding of the wire, the next coil winding begins in a continuous manner, and in such case there arises the danger of a short circuit at the point of breakaway of the coating.
An object of this invention is therefore to provide a tensioning device for a coil winding machine which overcomes the above-mentioned drawbacks of the conventional devices.